I am having the same issue. My W2 does not have any amount in Box 18, but I did pay local taxes in Box 19. I already submitted my taxes for 2020 successfully back in March 2021. I found another form to add to my taxes and now when I try to amend my taxes, TurboTax will not let me submit for the box 19 error. I have typed it in exactly as my W2.
